Boosting oversight of such firms has been a long-standing priority for the commission

WASHINGTON—The Securities and Exchange Commission is adding 100 compliance examiners devoted to inspecting financial planners, money managers and other investment advisers, the largest increase in recent years, according to people familiar with the matter.

The 20% increase in the number of inspectors, to about 630, is aimed at addressing the agency’s inability to conduct frequent inspections of investment advisers, these people said.